Biomarkers of toxic response to low nicotine cigarette smoke. Exposure to tobacco smoke (mainstream and environmental) is a leading cause of death in the US. Cigarette smoke is an extremely complex mixture including numerous toxic polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene (B[a]P) and nitrosamines such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in both the mainstream and sidestream (environmental) smoke fractions. This has stimulated the concept that reduced exposure products (PREPs) such as those with reduced nicotine content will provide a safer alternative. The Institute of Medicine has suggested that products, which reduce harm, may be a feasible and justifiable public health policy, particularly for those who cannot or will not quit smoking. However, careful evaluation of these PREPs is necessary in order to characterize reductions in exposure to harmful substances, and to determine if there is an association between reduced exposure and reduced harm to health. One type of PREP, called Quest(R), uses genetically modified tobacco with lower nicotine levels to provide a means for smokers to "step down to become nicotine-free". Claims of less nicotine are often interpreted by smokers as meaning that the cigarette is less harmful. Nicotine is the primary addictive agent in cigarettes and previous research has shown that compensatory smoking occurs when smokers are switched to lower nicotine cigarettes. By taking larger and more frequent puffs, a smoker is exposed to more smoke and smoke particulates that contain PAHs and nicotine-derived nitrosamines. PAH levels vary among the different commercial cigarette brands. Quest(R) cigarettes contain significant levels of tar at each of the three nicotine levels that are available and so may contain similar amounts of toxins to regular cigarettes. Therefore, they have the potential to be a harm-increasing product. Existing biomarkers of exposure to cigarette smoke have concentrated on measurements of nicotine exposure (cotinine levels), and PAH exposure such as the analysis 1-hydroxypyrene and the urinary metabolite of NNK, (4- methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL)-glucuronide. The only toxic biological response biomarkers that have been used are urinary isoprostanes to monitor oxidative stress, and the analysis of B[a]P-derived DNA adducts in leukocytes. Therefore, there is a compelling need to devise and validate a more comprehensive panel of toxic biological response biomarkers that can be employed to provide insight into the differences between exposure to conventional cigarettes and those that have reduced nicotine content such as the Quest(R) cigarettes. This will make it possible to more effectively address whether the Quest(R) cigarettes are a harm-increasing product. We propose to build on recent exciting new biomarker studies to develop panels of in vivo urinary and exhaled breath condensate (EBC) toxic biological response biomarkers and to validate hydroxylated B[a]P derivatives as new exposure biomarkers. We hypothesize that these biomarker panels will make it possible to determine whether reduced nicotine cigarettes reduce the excretion of toxic biological biomarkers. The hypothesis will be tested in a within- subject, open-label design of 260 smokers who report not currently being interested in quitting, but interested in trying a new cigarette product under two Specific Aims. Aim 1: To determine how smoking cigarettes with progressive decreases in nicotine levels, using a Quest(R) step-down design, modulates excretion of exposure and toxic biological response biomarkers in urine and EBC when compared with normal cigarettes. Aim 2: To rigorously validate the observed changes in urinary and EBC exposure and toxic biological response biomarkers caused by smoking cigarettes with progressive decreases in nicotine levels using the Quest(R) non-step-down study design when compared with smoking normal cigarettes. PUBLIC HEALTH RELEVANCE: Exposure to tobacco smoke is a leading cause of death in the US. Cigarette smoke is an extremely complex mixture including numerous toxic and cancer-causes substances. This has stimulated the concept that reduced exposure products such as those with reduced nicotine content could provide a safer alternative. Smokers often interpret claims of lower nicotine as meaning that the cigarette is less harmful. We propose to establish a method to determine whether reduced nicotine cigarettes are in fact safer than normal cigarettes. A panel of biomarkers will be developed, which will show whether individuals have a toxic response to smoking low nicotine cigarettes and whether the toxic response is different from smoking conventional cigarettes.